Without limiting the scope of the invention, its background is described in connection with method and apparatus for gender selection.
When thinking of conceiving an offspring, most people often have a preference for a child having a particular gender. However, it is difficult to select or even influence the selection of the gender of an as yet not conceived offspring as many factors influence natural gender selection in human or other animal.
It has been known for years that gender, in mammals, is determined by the presence of XX chromosomes in females or one X chromosome and one Y chromosome in males (XY). Joining of sperm and egg during the fertilization process results in a zygote containing one chromosome from the female and one chromosome from the male. Only one type of egg results from the female, an egg containing a single X chromosome. But two types of sperm result from the male, one carrying a single X chromosome and one carrying a single Y chromosome. Since these two types of sperm are produced in almost equal numbers there is basically a 50-50 chance of conceiving one gender or the other if all other factors are equal since fertilization of an egg by an X-bearing sperm will lead to an XX zygote while fertilization of an egg by a sperm with a Y chromosome will lead to an XY zygote.
There are number of reasons for performing gender selection. Economically, gender selection can be seen in the dairy industry which prefers one sex in its livestock production system in order to increase management efficiency and productivity. Research in gender selection is an ongoing effort in the field of art, and many methods have been attempted to achieve the separation of X- and Y-chromosome bearing sperm.
For example, in the U.S. Pat. No. 5,346,990 titled “Sex-associated membrane proteins and methods for increasing the probability that offspring will be of a desired sex”, Spaulding described a method of sorting living cells based on DNA content. Here, mammalian sperm subpopulations enriched in X- or Y-sperm, e.g., X- and Y-enriched sperm-plasma-membrane vesicles. Substantially pure sex-associated membrane (SAM) proteins. Antibodies binding to X- or Y-SAM proteins, essentially free of antibodies binding to Y— or X-SAM proteins respectively, or to the H—Y antigen. Semen samples enriched for X- or Y-sperm. To obtain the population, a refined X sex-associated membrane protein is characterized by a higher band density on an SDS/PAGE of plasma membrane proteins prepared from X-enriched sperm subpopulations as compared to the corresponding band density on an SDS/PAGE of plasma membrane proteins prepared from whole sperm or prepared from Y-enriched sperm subpopulations; or a refined Y sex-associated membrane protein characterized by a higher band density on an SDS/PAGE of plasma membrane proteins prepared from Y-enriched sperm subpopulations as compared to the corresponding band density on an SDS/PAGE of plasma membrane proteins prepared from whole sperm or prepared from X-enriched sperm subpopulations.
Another example can be found in the U.S. Pat. No. 6,489,092 titled “Method for sex determination of mammalian offspring”. Briefly, a method for increasing the percentage of mammalian offspring of either sex which comprises contacting a semen sample with an antibody specific for the spermatozoa determinative of one sex and separating the spermatozoa from spermatozoa determinative of the other sex, the antibody being bound to a non-porous magnetic bead support having a diameter of 0.1 to 2 microns is taught.
Yet another example can be found in the U.S. Pat. No. 7,195,920. The '920 patent describes collection systems for cytometer sorting of sperm. This patent describes an improved flow cytometer system particularly adapted to use for sex-selected sperm sorting include enhanced sheath fluid and other strategies which minimize stress on the sperm cells, including a 2.9 percent sodium citrate sheath solution for bovine species and a HEPES bovine gamete media for equine species. Improved collection systems and techniques for the process are described in the '920 patent so that commercial applications of sperms samples as well as the resulting animals may be achieved.
Although techniques exist in the field to sort sperm cells bearing X or Y chromosome, all existing methods, save the flow cytometry method, have had only limited clinical or statistical success in controlling the sex of offspring. Further, the cytometry method, while fuctional, has a high cost, require expensive equipment and highly skilled technicians to operate and has the potential of induction of mutations. The present inventors recognize the limitation in the existing art and the desire to achieve sex-sorted sperm samples using inexpensive disposable components and substances.